Hydraulic spin-on fluid filters are well known in the art and are typically used for the purpose of filtering hydraulic working fluid in the hydraulic circuit of an engine and/or vehicle. Such hydraulic fluid filters typically comprise an end plate either stamped or cast of metal material. A cylindrical drawn metal canister is secured directly or indirectly to the end plate (e.g. indirect attachment can be done by way of a seaming lid, which also serves to retain an external seal) and a suitable filter element contained therein. The filter element often includes cylindrical pleated filter media, but may also be any other form of suitable filtering media. The end plate of the filter usually includes a central threaded hole which serves as means to provide at least one fluid port for the filter element and also provides a means for mounting and threadedly fastening the filter to the mounting adaptor of a fluid circuit. Examples of such fluid filters are shown for example in U.S. Pat. Nos. 5,906,740; 5,453,195; 5,490,930; 5,906,736; and 6,554,140. Since the present invention relates to improvements over these prior designs, and may be incorporated into these designs, the patents are hereby incorporated by reference.
As it pertains to high pressure spin-on type filters, there are several different considerations in the design of the filter. For example, the '740, '195 and '930 patents referenced above discuss the importance of having high strength to resist high pressure when in use (both burst strength and cyclical fatigue strength). It is also known to connect the end plate or base plate to the canister directly thereby avoiding the use of a separate seaming lid to facilitate a connection to reduce the number of parts. However, in doing so, a significant consideration when attaching the end plate directly to the cylindrical side wall of the canister is how best to torsionally lock the end plate to the canister since installation and removal of the filter requires spinning the canister and transferring torque from the canister to the end plate. This is necessary to drive the internal threading formed into the end plate onto and off the threaded stub of a mounting adaptor for the fluid circuit. One such technique, for example, is proposed in the '740 patent, as shown, for example, in FIGS. 8-10.